Lead formation, assembly strip test and singulation method

ABSTRACT

A method for testing integrated circuits (ICs) mounted on an assembly strip after lead formation and before separation from the assembly strip. The ICs are arranged in rows and columns on each assembly strip such that the sides of each IC are connected to leads extending from the assembly strip, and the ends of each IC are held by the assembly strip. The strips are loaded into the system and passed to a first station at which leads are cut and formed while the ends of each IC remain connected to the assembly strip. The assembly strips are then passed to a test apparatus that transmits test signals to the ICs through the formed leads. The IC devices are then separated from the assembly strip using a singulation apparatus, and the separated ICs are stored in tubes for delivery. Visual inspection is also performed at various stages.

FIELD OF THE INVENTION

[0001] This invention relates to integrated circuits, and moreparticularly to methods and automated systems for efficiently testingintegrated circuits.

BACKGROUND OF THE INVENTION

[0002] Molded IC devices are often assembled (packaged) on matrix-typelead frame structures in which the IC devices are arranged in multiplerows and columns, and then tested while connected to the matrix-typelead frame (i.e., before being singulated (separated) into individual ICdevices). As utilized herein, the term “assembly strip” is used todescribe the integral structure formed by such a matrix-type lead framestructure with IC devices packaged thereon. Assembly strips facilitatelow-cost automated production by allowing several IC devices to betested simultaneously (i.e., in parallel), thereby reducingmanufacturing time and costs.

[0003] FIGS. 1(A) through 1(C) are perspective views showing aconventional process of assembling IC devices using a lead frame 100,which is simplified for descriptive purposes. Referring to FIG. 1(A),lead frame 100 is etched or stamped from a thin sheet metal strip, andincludes side rails 110, cross rails 120, and multiple die attachregions 130. Each die attach region 130 includes a die attach platform132 connected to side rails 110 by tie bars 135, and patterns of narrowleads 140 that radiate inward from side rails 110 and cross rails 120toward die attach platform 132. Note that leads 140 do not contact dieattach platform 132. During a first stage of the bonding process that isshown in FIG. 1(A), an IC die 150 is mounted onto each die attachplatform 132 using, for example, an epoxy resin. A pattern of die bondpads 152 are provided on an upper surface of IC die 150 that areelectrically connected to the integrated circuit formed thereon. Asshown in FIG. 1(B), after IC die 150 is secured to die attach platform132, each die attach platform 152 is electrically connected to acorresponding lead 140 by a fine-diameter gold bond wire 160 usingwell-established wire bond techniques. Subsequently, as indicated inFIG. 1(C), die attach platform 132, the inner ends of leads 140, die150, and bond wires 160 are covered with a thermoset plastic casing 170during a transfer molding operation. Note that a portion of each lead140 is exposed along the sides of casing 170. The integral structureincluding lead frame 100 and the fully packaged IC device is referred tobelow as assembly strip 105.

[0004] FIGS. 2(A) through 2(C) show a conventional process forfunctional testing, lead formation, and singulation (i.e., separation ofindividual IC devices 200 from assembly strip 105), which is performedafter the assembly process shown in FIGS. 1(A) through 1(C). First, asshown in FIG. 2(A), the conventional process includes cutting leads 140such that they are separated from side rails 110 and cross rails 120 oflead frame 100. Note that IC devices 200 remain connected to assemblystrip 105 by tie bars 135, and that leads 140 remain flattened (i.e., inplane with side rails 110 and cross rails 120 of lead frame 100). Asshown in FIG. 2(B), functional testing is then performed during whichtest signals are transmitted from a tester 210 to IC devices 200 viaprobes 215, which are pressed against leads 140 by a suitable mechanism.Note that functional testing is performed while leads 140 are flat(i.e., in the plane defined by lead frame 100). Finally, as indicated inFIG. 2(C), lead forming and singulation is performed to produceindividual IC devices 200 having fully formed leads 140. Aftersingulation, lead frame 100 is discarded.

[0005] A problem with the conventional testing and singulation processshown in FIGS. 2(A) through 2(C) is that three separate systems arerequired to perform each of lead cutting (FIG. 2(A)), functional testing(FIG. 2(B)), and singulation (FIG. 2(C)), thereby increasing the totalproduction cost per IC device 200. Further, transferring assembly strips105 between these separate systems inevitably leads to accidents thatdamage IC devices 200, further increasing production costs.

[0006] What is needed is an efficient and cost effective system andmethod for performing functional testing, lead formation, andsingulation of IC devices that avoids the cost and handling issuesassociated with the conventional methods described above.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to a method for processing andtesting ICs mounted on an assembly strip in which both functional andvisual lead inspection are performed after cutting and forming theleads, and prior to singulation (i.e., prior to separation of theindividual ICs from the assembly strip). Accordingly, the presentinvention facilitates functional testing, lead formation, andsingulation using a single, relatively inexpensive system, therebyreducing overall production costs when compared to conventional methodsfor performing these procedures. Further, because the assembly stripsremain attached to a single system throughout functional testing, leadformation, and singulation, the present invention also minimizeshandling by eliminating transfer between independent systems, therebyreducing the costs associated with damage caused during such transfers.

[0008] Each assembly strip processed in accordance with the presentinvention includes multiple rows and columns (e.g., 5×12) of ICs thatare mounted on a matrix-type lead frame. In one embodiment, the leadframe includes IC mounting regions made up of a die attach platform thatis connected at opposite ends to the lead frame, and parallel leadsextending from opposing sides of the die attach platform to lead tiebars of the lead frame. An IC is mounted on each die attach platform andconnected (e.g., using wire bonding techniques) to the leads locatedadjacent to the die attach platform. Subsequently, packaging material(e.g., thermoset plastic) is formed over the IC, bonding wires and dieattach platform.

[0009] In accordance with a disclosed embodiment of the presentinvention, a method for processing ICs mounted on assembly stripsutilizes a lead length cut/form apparatus, a functional test apparatus,and a singulation apparatus. After the IC dies are mounted on theassembly strip, they are loaded into magazines and systematically movedby an onloader to a conveyor, which moves the assembly strips to thelead length cut/form apparatus. The lead length cut/form apparatus cutsthe leads connected to the package of each IC, preforms (i.e., bends)the leads, and forms the leads into a desired final form withoutseparating the ICs from the assembly strip. The assembly strips are thenpassed to the functional test module in which probes (e.g., pogo pins)are pressed against the fully formed leads and functional tests aretransmitted to the ICs from a tester. Visual inspection of the leads isthen performed to identify defective leads, e.g., damaged leads, bentleads, or missing leads. After functional and visual testing, theassembly strips are passed to a singulation apparatus that separates theICs from the assembly strip frame, and to an offloader that loads theseparated ICs into storage tubes. An optional second visual inspectionmay be performed after singulation and prior to loading to detectpackage defects that may have occurred during the testing andsingulation operations, or during preceding processes.

[0010] In accordance with an aspect of the present invention, the leadcut/form process and singulation process are performed using a singledrive apparatus, thereby reducing costs by eliminating the need forseparate drive mechanisms for these two operations. Note that thefunctional testing process, which is performed between the lead lengthcut/form and singulation processes, is provided with a separateball-screw drive that facilitates testing of the ICs. A conveyor isutilized to automatically pass each assembly strip from the lead lengthcut/form process to the functional test process, and from the functionaltest process to the singulation process, thereby minimizing IC damagecaused by transporting the assembly strips between separate systems.

[0011] In accordance with another aspect of the present invention,functional testing is performed using a stationary anvil and a probeassembly that is moved toward and away from the anvil by the ball-screwdrive. The anvil includes a trough and a pair of rails that hold the ICdevices during testing. The probe assembly includes probes (e.g., pogopins) that are pressed against the leads of the IC devices, which aresupported by the rails to prevent damage. The probes are arranged toinclude a first set positioned to contact a portion of the leads locatedon top of the rails when the probe assembly is initially moved towardthe anvil, and a second set positioned to contact the feet of the leadswhen the probe assembly is moved further toward the anvil. Accordingly,the functional testing module facilitates functional testing whilepreventing damage to the leads, thereby reducing the number of systemsneeded to perform the testing and singulation process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

[0013] FIGS. 1(A), 1(B), and 1(C) are perspective views showing aconventional IC device assembly process;

[0014]FIG. 2(A), 2(B), and 2(C) are perspective views showing aconventional process for functional testing, lead formation, andsingulation of IC devices using an assembly strip;

[0015]FIG. 3 is a block diagram showing a system for IC device leadformation, functional test, and singulation according to an embodimentof the present invention;

[0016]FIG. 3A is a simplified side view depicting a portion of thesystem shown in FIG. 3;

[0017]FIG. 4 is partial plan view showing an exemplary assembly striputilized in accordance with an embodiment of the present invention;

[0018] FIGS. 5(A) and 5(B) are plan and side section views showing an ICdevice mounted on the assembly strip of FIG. 4;

[0019] FIGS. 6(A), 6(B), and 6(C) are simplified cross-sectional sideviews showing portions of a lead length cut/form apparatus of the systemshown in FIG. 3;

[0020] FIGS. 7(A), 7(B) and 7(C) are end views showing the assemblystrip of FIG. 4 showing the lead length cut/form process;

[0021]FIG. 8 is a plan view showing an exemplary IC device after leadformation is completed; and

[0022] FIGS. 9(A) and 9(B) are side and partial front views,respectively, showing a functional test apparatus utilized in the systemof FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

[0023]FIG. 3 is a block diagram showing a system 300 for processing andtesting integrated circuits (ICs) that are mounted on assembly strips305. System 300 generally includes a conveyor mechanism (workholder)301, a drive apparatus 310, a lead length cut/form apparatus 320, afunctional test apparatus 330, and a singulation apparatus 350.

[0024] Conveyor 301 transports assembly strips 305 to lead lengthcut/form apparatus 320, from lead length cut/form apparatus 320 tofunctional test apparatus 330, and from functional test apparatus 330 tosingulation apparatus 350. Note that conveyor 301 may be separated intosegments that feed into each of the apparatus, or may be formed using acontinuous belt. A system controller (not shown) controls the speed andposition of conveyor 301.

[0025]FIG. 3A is a simplified side view depicting selected functionalaspects of system 300. As indicated in FIG. 3A, conveyor 301 is mountedon a base 309 that supports each of lead length cut/form apparatus 320,functional test apparatus 330, and singulation apparatus 350, and feedsassembly frames through system 300 (e.g., in a horizontal directionindicated by the X arrow). Drive apparatus 310 is mounted over base 309,and includes a motor 315 for turning a cam mechanism (depicted asincluding a shaft 313 and cam wheels 314) that is utilized to operateboth functional test apparatus 330 and singulation apparatus 350. Inparticular, lead length cut/form apparatus 320 includes a stationary(first) portion 320A rigidly mounted on base 309, and a movable (second)portion 320B that is reciprocated toward and away from stationaryportion 320A (i.e., in the vertical direction indicated by arrow Y)through contact with the cam mechanism of drive apparatus 310 when thecam mechanism is turned by motor 315. Similarly, singulation apparatus350 includes a stationary (first) portion 350A mounted on base 309, anda movable (second) portion 350B contacting the cam mechanism of driveapparatus 310 such that movable portion 350B is reciprocated toward andaway from stationary portion 350A when the cam mechanism is turned.Functional test apparatus 330, which is located between lead lengthcut/form apparatus 320 and singulation apparatus 350, includes astationary (first) portion 330A mounted on base 309, and a movable(second) portion 330B mounted over stationary portion 330A. Note thatmovable portion 330B is reciprocated toward and away from stationaryportion 330A by a separate drive 330C to facilitate IC testingprocedures.

[0026] FIGS. 4, 5(A) and 5(B) show assembly strip 305 in additionaldetail.

[0027]FIG. 4 is a partial view showing opposing ends of exemplaryassembly strip 305. Assembly strip 305 includes a matrix-type lead frame400 including side rails 410 and cross rails 420, and includes severalrows of IC mounting regions 430 located between cross rails 420, eachmounting region 430 including one IC device 440 mounted thereon. In oneembodiment, each row includes five (5) mounting regions 430, andassembly strip 305 includes twelve (12) columns.

[0028] FIGS. 5(A) and 5(B) are plan and cross-sectional side views,respectively, showing one mounting region 430 in additional detail.Referring to FIG. 5(B), each IC device 440 includes a die 500 mounted ona die attach platform 432, with die 500 being is electrically connectedto leads 435 by bond wires 510. A thermoplastic IC package 520 is formedover die 500, bond wires 510, and ends of leads 435 using techniquesdescribed above with reference to FIGS. 1(A) through 1(C). Referring toFIG. 5(A), each IC device 440 is mounted and packaged such that ends 522of each IC package 520 are secured to connection structures 422 of crossrails 420 by tie bars (not shown). Similarly, leads 435 extend betweensides 524 of each IC package 522 and lead tie bars 415 of assembly strip305. Note that when assembly strip 305 is formed (i.e., by stamping oretching a metal sheet according to known methods), leads 435 areintegrally connected to lead tie bars 415.

[0029] Referring back to FIG. 3, in one embodiment assembly strips 305are introduced into system 300 using a loading apparatus (ONLOADER) 302.In one embodiment, onloader 302 includes a first magazine (MAG) 303-1and a second magazine 303-2 that respectively store multiple assemblystrips 305, and a pick-and-place mechanism 306 for moving assemblystrips 305 from magazines 303-1 and 303-2 onto conveyor 301 using knowntechniques. From onloader 302, conveyor 301 transfers assembly strips305 to cut/form apparatus 320, functional test apparatus 330, andsingulation apparatus 350, respectively, for processing in the orderdescribed below.

[0030] Referring to center-left region of FIG. 3, according to anembodiment of the present invention, lead length cut/form apparatus 320includes a lead length cut mechanism 322, a lead preform mechanism 324,and a lead form mechanism 326. Lead length cut mechanism 322, leadpreform mechanism 324, and lead form mechanism 326 include movableportions that are reciprocated by drive apparatus 310, and aresuccessively arranged along the path of conveyor 301 such that leads 435(see FIG. 5(A)) of each assembly strip 305 are successively cut,preformed, and formed in the manner described below.

[0031] FIGS. 6(A), 6(B), and 6(C) are simplified cross-sectional sideviews showing representative portions of lead length cut mechanism 322,lead preform mechanism 324, and lead form mechanism 326, respectively,in additional detail. In one embodiment, each mechanism is formed as aseparate unit mounted on base 309. Those of ordinary skill in the artwill recognize that two or more of these mechanisms may be combined toperform the cutting, preforming, and forming processes using less thanthree separate mechanisms. Further, additional mechanisms may be addedto facilitate a more gradual lead forming process.

[0032] Referring to FIG. 6(A), lead length cut mechanism 322 includes ananvil 610, a lead length cut die 615, and a lead length cut punch 620.Anvil 610 is mounted on base 309 and supports package 520 of IC device440 during the lead length cutting process. Lead length cut die 615 isalso mounted on base 309, and includes upper edges 617 that supportleads 435, and serve as one part of the lead cutting mechanism. Leadlength cut punch 620 is movably mounted over anvil 610, and is connectedto the cam mechanism of drive apparatus 310 such that it reciprocates invertical direction (indicated by the two-headed arrow Y). Lead lengthcut punch 620 includes lower edges 622 that serve as the second part ofthe lead cutting mechanism. During the lead length cutting process, theassembly strip is moved such that IC device 440 is located between anvil620 and lead length cutting punch 620 (i.e., the assembly strip is movedperpendicular to the page), and then punch 620 is moved downward (towarddie 615) to sever the end of each lead 435. Punch 620 is then movedupward, and the assembly strip is moved to position another IC devicefor the lead length cutting process.

[0033]FIG. 6(B) shows lead preform mechanism 324, which includes a lower(first) anvil 630, a lead preform punch 640, and an upper (second) anvil645. Lower anvil 630 is mounted on base 309 and supports package 520 ofIC device 440 during the lead preforming process. Lower anvil 630 alsoincludes shoulders 632 that support a portion of leads 435 locatedadjacent to package 520, and chamfered surfaces 634 that have, forexample, a 45 downward slope relative to the plane defined by theassembly strip. Lead preform punch 640 is movably mounted over anvil610, and is connected to the cam mechanism of drive apparatus 310 suchthat it reciprocates in vertical direction. Lead preform punch 640includes lower chamfered surfaces 644 that have the same slope aschamfered surfaces 632 formed on lower anvil 630, and are positioneddirectly over chamfered surfaces 632. Upper anvil 645 is slidablymounted on preform punch 640, and includes shoulders 647 that cooperateswith shoulders 632 of lower anvil 630 to support the portion of leads435 located near package 520 during the preform process. During the leadpreform process, the assembly strip is moved such that IC device 440 islocated between lower anvil 630 and lead length cutting punch 640 (i.e.,perpendicular to the page), and then punch 640 is moved downward (towardlower anvil 630). First, shoulders 647 of upper anvil 645 contact theportions of leads 435 located adjacent to package 520 (i.e., these leadportions are pinched between shoulders 632 and shoulders 647). Next,preform punch 640 moves downward to bend leads 435 at a 45 angle betweenchamfered surface 634 and chamfered surface 644. Punch 640 is then movedupward, and the assembly strip is moved to position another IC devicefor the lead preform process.

[0034]FIG. 6(C) shows lead forming mechanism 326, which includes a lower(first) anvil 650, an upper (second) anvil 660, and a cam portion 670.Lower anvil 650 is mounted on base 309 and includes a trough thatreceives and supports package 520 of IC device 440 during the leadforming process. Lower anvil 650 also includes a pair of rails 652 thatsupports a portion of leads 435 located adjacent to package 520. Upperanvil 660 is movably mounted over anvil 610, and is connected to the cammechanism of drive apparatus 310 such that it reciprocates in verticaldirection, and includes shoulders 662 that cooperates with rails 652 tohold portions of leads 435 located near package 520 during the leadforming process. Cam portion 670 is rotatably connected to upper anvil660, and includes a cam form pad 672 that contacts and bends the freeends of leads 435 during the lead forming process to form feet at thefree ends. During the lead forming process, the assembly strip is movedsuch that IC device 440 is located between lower anvil 650 and upperanvil 660, and then upper anvil 660 is moved downward. First, shoulders662 of upper anvil 660 contact the portions of leads 435 locatedadjacent to package 520 (i.e., these lead portions are pinched betweenshoulders 662 and rails 652). Next, cam portion 670 rotates inward suchthat cam form pads 672 press leads 435 against rails 652, therebybending leads 435 between cam form pads 672 and rails 652 to form feet.Upper anvil 660 and cam portion 670 are then moved upward, and theassembly strip is moved to position another IC device for the leadforming process.

[0035] FIGS. 7(A), 7(B) and 7(C) are end views showing assembly strip305 as it is processed by lead length cut/form apparatus 320 (shown inFIG. 3). Note that each of lead length cut mechanism 322, lead preformmechanism 324, and lead form mechanism 326, which are described abovewith reference to FIGS. 6(A) through 6(C), include multiple processingsites for cutting, preforming, or forming the leads of one or more rowsof IC devices simultaneously. Specifically, as shown in FIG. 7(A), leads435 of one row of IC devices 440 are cut by lead length cut mechanism322 (FIG. 6(A)) at a point adjacent to lead tie bars 415 (i.e., suchthat each lead 435 becomes a cantilever structure with a fixed endsupported by IC package 520). Next, as shown in FIG. 7(B), leads 435 arebent downward relative to package 520 (i.e., out of plane PI defined byassembly strip 305) by lead preform mechanism 324 (FIG. 6(B)) at anangle of approximately 45. Finally, as shown in FIG. 7(C), the free endsof leads 435 are bent by lead form mechanism 326 (FIG. 6(C)) to formfeet 437 that define a second plane P2 located below plane P1. Becauseall three procedures shown in FIGS. 7(A) through 7(C) (i.e., lead cut,lead preform, and lead form) are performed by apparatus 320 beforefunctional testing, total manufacturing costs are reduced becauseseparate lead cutting and lead forming apparatus are not required. Thatis, total cost is reduced because each of lead length cut mechanism 322,lead preform mechanism 324, and lead form mechanism 326 are driven by asingle mechanism (i.e., drive apparatus 310), instead of two or moredrive mechanisms that are required using conventional methods. Further,because lead length cut mechanism 322, lead preform mechanism 324, andlead form mechanism 326 are linked by conveyor 301 such that assemblystrips 305 are automatically transferred between these mechanisms,damage to leads 435 that can occur during transportation between twoseparate systems is also avoided, further reducing total productioncosts.

[0036]FIG. 8 is an enlarged plan view showing IC 440 after the cut/formprocedure performed by apparatus 320 is completed. Note that leads 435are separated from lead tie bars 415, but ends 522 of IC device 440remains connected to connection structures 422 of assembly strip 305.Accordingly, IC devices 440 remain fixedly connected to assembly strip305 throughout the lead cutting and forming process, therebyfacilitating automated testing (described below).

[0037] Returning to FIG. 3, after lead formation, assembly strips 305are then passed via conveyor 301 to functional test apparatus 330.Functional test apparatus 330 includes a separate ball-screw drive 332,a test module 334, and tester (e.g., a computer or workstation) 336.

[0038] FIGS. 9(A) and 9(B) are side and partial front views showingfunctional test apparatus 330 in additional detail.

[0039] Referring to FIG. 9(A), functional test apparatus 330 includes ananvil 910 that is mounted on base 309. Mounted over anvil 910 is a probeassembly 920, which includes a lower plate 924 that supports a probearray 930. Mounted above lower plate 924 is a non-conductiveintermediate plate 926 and a non-conductive top plate 928. Sandwichedbetween intermediate plate 926 and top plate 928 is a printed circuitboard (PCB) 940 including a socket 945 from which a cable 948 extendsbetween PCB 940 and tester 336. Probe array 930 extends from a lowersurface of lower plate 924, and includes probes (e.g., dual spring pogopins) 935 having one end extending toward anvil 910, and a second endpressed against corresponding contact pads (not shown) formed on a lowersurface of PCB 940.

[0040] Referring to FIG. 9(B), anvil 917 includes several troughs 915and pairs of rails 917, each pair of rails 917 being located along theoutside edges of an associated trough 915. Troughs 915 are shaped toreceive and support the lower package body of IC devices 440, and rails917 are shaped to support a portion of leads 435 located adjacent to thepackage body during functional testing, which is described below. Notethat the bent portion of leads 435 (i.e., including feet 437) extendover rails 917 such that feet 437 are positioned over lands 919.

[0041] During operation, conveyor 301 (shown in FIG. 3) pushes assemblystrip 305 in the X direction such that a group of IC devices 440 arepositioned on anvil 917 with leads 435 located under probes 935. Theball-screw drive 332 moves probe assembly 920 downward towards anvil 910such that the ends of probes 935 contact leads 435. Once the probeassembly is fully lowered, the system controller sends a “start test”signal to the tester 336 to initiate the functional test. As indicatedin FIG. 9(B), in one embodiment, probes 935 include a first set 935Awhich contacts an upper portion of leads 435 (i.e., adjacent the packagebody), and a second set 935B that subsequently contacts feet 437.Because first probe set 935 contacts leads 435 adjacent to the packagebody, IC devices 440 are securely held in position before second probeset 935B contacts feet 437. Note that first probe set 935A serves bothto hold IC devices 440 during testing, and to provide enhancedelectrical connection between the tester (not shown) and IC devices 440.Accordingly, functional test apparatus 330 facilitates testing ICdevices 440 after leads 435 are fully formed, and with minimal risk ofdamaging or bending leads 435. Test signals are then transmitted to andfrom tester 336 via cable 948, socket 945, PCB 940, and probes 935 toleads 435. As discussed above, leads 435 are connected, for example, bybond wires to the IC die packaged therein, thereby facilitatingfunctional testing of the IC die. An optional marking system (not shown)may be used to mark IC devices 440 that fail functional testing. Uponcompleting functional testing of the group of IC devices 440, tester 336sends an “end of test” signal to the system controller. Ball-screw drive332 then raises probe assembly 920, and the conveyor pushes assemblystrip 305 to position a new group of IC devices 440 under probes 935.This functional testing process is then repeated until all IC devices440 on assembly strip 305 are tested.

[0042] Note that functional test apparatus 330 is described above astesting groups of ten IC devices 440 (i.e., in a so-called “2 UP X 5”arrangement). Accordingly, multiple IC devices 440 are testedsimultaneously, thereby minimizing overall production costs. Of course,other arrangements may be utilized to test a different number or patternof IC devices.

[0043] Returning to FIG. 3, upon leaving functional test apparatus 330,assembly strips 305 pass through an optional lead vision inspectionstation 340 including a first vision system 342 that checks the leads ofeach IC device 440 using known techniques. In particular, vision system342 checks for damaged leads, bent leads, missing leads, or short leads.

[0044] After lead vision inspection, assembly strips 305 are passed tosingulation apparatus 350. In one embodiment, singulation apparatus 350utilizes standard equipment that includes an anvil and a singulation diemounted on the system base, and a stripper and a punch movably mountedover the anvil and connected to the cam mechanism of drive apparatus 310(see FIG. 3A). Similar to structures described above, the anvil includesa package support, and the singulation die supports the rails of theassembly strip. After positioning the assembly strip, the stripper ismoved downward against the rails, and the punch then pushes the packagedownward. Referring to FIG. 8, this downward force breaks the tie bars(not shown) connecting ends 522 of each IC device 440 to connectingstructures 422 of assembly strip 305, thereby separating IC device 440from assembly strip 305. Referring to FIG. 3, separated lead frames arepassed into a scrape lead frame (L/F) chute 352, and the separated ICdevices 440 are passed to a buffer station 360.

[0045] Buffer station 360 includes a second vision system 362 thatperforms an automated inspection of each IC device 440 using knowntechniques. In particular, vision system 362 checks each IC device 440for package surface damage, voids, and device markings. Buffer station360 then segregates the IC devices for manipulation by an offloadingmechanism 370. In particular, buffer station 360 routes the “good” ICdevices to a chute feeding into a first set of storage tubes 380.Alternatively, buffer station 360 routes “bad” IC devices (i.e., rejectsfrom functional test, vision system 342, or vision system 362) to achute feeding into a second set of storage tubes 390.

[0046] Although the present invention has been described with respect tocertain specific embodiments, it will be clear to those skilled in theart that the inventive features of the present invention are applicableto other embodiments as well, all of which are intended to fall withinthe scope of the present invention.

1. An assembly strip test method for testing integrated circuits mountedon a matrix-type lead frame defining a plane, the method comprising:cutting and forming leads of the integrated circuits such that the leadsare bent out of the plane defined by lead frame, wherein the integratedcircuits remain connected to the lead frame after the leads are formed;performing functional testing on the integrated circuits by transmittingtest signals onto the formed leads of the integrated circuits; andseparating the tested integrated circuits from the lead frame.
 2. Themethod according to claim 1, further comprising: moving the lead frameon a conveyor from a first apparatus for cutting and forming the leadsto a second apparatus for function testing the integrated circuits; andmoving the lead frame on the conveyor from the second apparatus to athird apparatus for separating the integrated circuits from the leadframe.
 3. The method according to claim 1, further comprisingautomatically inspecting the leads of the integrated circuits afterperforming functional testing and before separating the integratedcircuits from the lead frame.
 4. The method according to claim 1,wherein cutting and forming the leads comprises cutting the leads usinga first mechanism, preforming the leads using a second mechanism, andthen forming the leads into a final form using a third mechanism.
 5. Themethod according to claim 4, wherein cutting the leads comprisessupporting a package body of the integrated circuit and positioning theleads of the integrated circuit between a stationary die and a movablepunch, and then moving the movable punch toward the stationary die, andwherein the stationary die includes a first edge, and the movable punchincludes a second edge positioned over the first edge such that thefirst and second edges cut the leads when the movable punch is movedtoward the stationary die.
 6. The method according to claim 4, whereinpreforming the leads comprises supporting a package body of theintegrated circuit and positioning the leads of the integrated circuitbetween a stationary anvil and a movable structure including a preformpunch and a second anvil slidably mounted on the preform punch, andmoving the movable structure toward the stationary anvil, wherein thefirst anvil includes a first shoulder for supporting the leads, and thesecond anvil includes a second shoulder positioned such that portions ofthe leads located adjacent to a package of the integrated circuit areheld between the first and second shoulders when the second anvil ismoved toward the first anvil, and wherein the first anvil includes afirst chamfered surface, and the preform punch includes a secondchamfered surface arranged such that the leads are bent between thefirst and second chamfered surfaces when the preform punch is movedtoward the first anvil.
 7. The method according to claim 4, wherein theforming the leads into the final form comprises supporting a packagebody of the integrated circuit and positioning the leads of theintegrated circuit between a stationary anvil and a movable structureincluding a second anvil and a lead forming portion rotatably connectedto the second anvil, and moving the movable structure toward thestationary anvil, wherein the first anvil includes a rail for supportingthe leads, and the second anvil includes a shoulder positioned such thatportions of the leads located adjacent to a package of the integratedcircuit are pinched between the rail and the shoulder when the secondanvil is moved toward the first anvil, and wherein the lead formingportion includes a cam form pad arranged such that the leads are formedbetween the cam form pad and the rail when the lead forming portion isrotated relative to the second anvil.
 8. The method according to claim1, further comprising automatically moving the matrix-type lead framefrom a first apparatus for cutting and forming the leads of theintegrated circuits to a second apparatus for performing functionaltesting using a conveyor.
 9. The method according to claim 8, whereinfunctional testing the integrated circuits comprises: moving thematrix-type lead frame such that one or more integrated circuits arepositioned between a stationary anvil and a movable probe assembly;moving the movable probe assembly toward the stationary anvil, whereinthe probe assembly includes a probe array having a plurality of probesarranged such that the probes contact the leads when the probe assemblyis moved toward the anvil by the ball-screw drive; and transmitting testsignals to the probes.
 10. The method according to claim 9, whereinmoving the movable probe assembly comprises contacting a base portion ofeach lead located adjacent to a package of the integrated circuit usinga first set of probes when the probe assembly is moved a first distancetoward the anvil, and contacting a foot of each lead using a second setof probes when the probe assembly is moved a second distance toward theanvil.
 11. The method according to claim 1, further comprisingautomatically moving the matrix-type lead frame from a first apparatusfor functional testing the integrated circuits to a second apparatus forseparating the tested integrated circuits from the lead frame using aconveyor.
 12. The method according to claim 11, wherein separating theintegrated circuits comprises positioning one or more integratedcircuits between a stationary anvil and a movable structure including astripper and a punch, and then moving the movable structure toward thestationary anvil such that the stripper pinches a leadframe of theassembly strip against the stationary anvil, and the punch pushes theintegrated circuit such that the integrated circuit is separated fromthe leadframe when the stripper and punch are moved toward the anvil.13. A method for testing integrated circuits formed on an assemblystrip, the assembly strip including a leadframe defining a plane and aplurality of integrated circuits mounted on the lead frame, eachintegrated circuit being electrically connected to a plurality of leadsextending between the integrated circuit and the leadframe, the methodcomprising: cutting and forming the leads of each integrated circuitsuch that the leads are bent away of the plane defined by the assemblystrip; and functional testing the integrated circuits using a pluralityof probes that are arranged to contact the cut and formed leads.
 14. Themethod according to claim 13, further comprising automatically movingthe lead frame from a first apparatus for cutting and forming the leadsof the integrated circuits to a second apparatus for performingfunctional testing using a conveyor.
 15. The method according to claim13, wherein cutting and forming the leads comprises cutting the leadsusing a first mechanism, preforming the leads using a second mechanism,and then forming the leads into a final form using a third mechanism.16. The method according to claim 15, further comprising driving thefirst, second, and third mechanisms using a single drive apparatus. 17.The method according to claim 13, further comprising automaticallymoving the matrix-type lead frame from a first apparatus for functionaltesting the integrated circuits to a second apparatus for separating thetested integrated circuits from the lead frame using a conveyor.
 18. Amethod for testing integrated circuits formed on an assembly strip, theassembly strip including a lead frame defining a plane and a pluralityof integrated circuits connected to the lead frame, each integratedcircuit including a package body housing an integrated circuit chip thatis electrically coupled to a plurality of leads extending from thepackage body, the method comprising: forming the leads such thatportions of the leads are bent out of the plane defined by the leadframe; and functional testing the integrated circuits by moving the leadframe such that one or more integrated circuits are positioned between astationary anvil and a movable probe assembly, moving the movable probeassembly toward the stationary anvil, and transmitting test signals tothe probe assembly, wherein the probe assembly includes a probe arrayhaving a plurality of probes arranged such that the probes contact theleads when the probe assembly is moved toward the anvil.
 19. The methodaccording to claim 18, wherein moving the movable probe assemblycomprises contacting a base portion of each lead located adjacent to apackage of the integrated circuit using a first set of probes when theprobe assembly is moved a first distance toward the anvil, andcontacting a foot of each lead using a second set of probes when theprobe assembly is moved a second distance toward the anvil.
 20. Themethod according to claim 18, further comprising automatically movingthe lead frame from a first apparatus for cutting and forming the leadsof the integrated circuits to a second apparatus for performingfunctional testing using a conveyor.